1. Field of the Invention
The present invention relates to a method and apparatus of treating ferromagnetic amorphous alloys to improve the magnetic properties and to avoid annealing embrittlement thereof, and more particularly to a method and apparatus of continuous dynamic Joule heating treatment.
2. Brief Description of the Prior Art
Ferromagnetic amorphous alloys have been widely used in many applications such as distribution transformers, magnetic shielding, security tape, etc. For the above applications, ferromagnetic amorphous alloys are usually made in the form of a long ribbon with desired width and thickness. The ribbons of such alloys must be heat treated before their magnetic applications. Iron base amorphous alloys are suitable for commercial mass production and applications because of their high saturation magnetization and relatively low cost. However an undesired annealing embrittlement occurs in the process of a conventional furnace annealing. This will effect the applications of the ferromagnetic amorphous alloys.
In U.S. Pat. No. 4,288,260 issued in September 1981, Senno et al proposed a dynamic annealing method of passing the amorphous ribbon over a hot body. Another heating process to pass an amorphous ribbon over a hot block heated by a quartz line heater was disclosed in U.S. Pat. No. 4,482,402 by Taub. None of these prior art methods could provide dynamic Joule heating to improve the magnetic properties of the ferromagnetic amorphous alloys.